Diaphragmatic blood flow in the dog

Author:

Bark H.,Scharf S. M.

Abstract

In anesthetized mongrel dogs we measured the blood flow in the left phrenic artery (Qdi), using an electromagnetic flow probe, before and during supramaximal phrenic nerve stimulation (pacing). This was done at constant respiratory rate (24/min) but at three different stimulation frequencies at a duty cycle of 0.4 (20, 50, and 100 Hz) and at three different duty cycles at a stimulation frequency of 50 Hz (duty cycle = 0.2, 0.4, and 0.8). Qdi was unchanged during diaphragm contraction until transdiaphragmatic pressure (Pdi) was greater than approximately 11 cmH2O, whereafter it began to decrease, reaching zero at Pdi approximately 20 cmH2O. Thus, when Pdi was greater than 21 cmH2O, all flow occurred during relaxation. Qdi averaged over the entire respiratory cycle (Qt) was less at duty cycle = 0.8 than under the other conditions. This was because of decreasing length of relaxation phase rather than a difference of relaxation phase flow (Qr), which was maximal during all conditions of phrenic stimulation. During pacing-induced fatigue, Qt actually rose slightly as Pdi fell. This was due to an increase in contraction phase flow while Qr remained constant. The relationship between Qt and tension-time index was not unique but varied according to the different combinations of duty cycle and stimulus frequency.

Publisher

American Physiological Society

Subject

Physiology (medical),Physiology

Cited by 21 articles. 订阅此论文施引文献 订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献

1. Neurovascular Proximity in the Diaphragm Muscle of Adult Mice;Microcirculation;2012-04-24

2. Relaxation of diaphragm muscle;Journal of Applied Physiology;1999-10-01

3. Regulation of ventilatory muscle blood flow;Journal of Applied Physiology;1996-10-01

4. Theophylline alters distribution of blood flow to respiratory muscles.;American Journal of Respiratory and Critical Care Medicine;1994-10

5. Phrenic blood flow in cats with a closed abdominal cavity;Bulletin of Experimental Biology and Medicine;1992-01

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